Wikipedia:Blogs as sources

Are blogs usable as sources in Wikipedia articles? It depends on the blog in question, it depends on the article in question, and it depends on what information is going to be used. There are three major policies, guidelines, and pages that cover this.

What is a blog?Edit

A blog is simply a website that commonly organizes its contents into "updates" that are posted in a given order, with the newest content frequently "first", at the top of given page. Each "update" is often a separate web page on the website. Many blogs allow readers of the online updates to post comments. A blog is no different from any other website, except in its structure, layout, and formatting.

Relevant policy pagesEdit

To check if a specific "blog" counts as a reliable source for your purposes, refer to these pages. These are excerpts from the April 13th, 2009 versions, for convenience:

Reliable sources
Material about living persons must be sourced very carefully. Without reliable third-party sources, it may include original research and unverifiable statements, and could lead to libel claims. See Wikipedia:Libel.
Material about living persons available solely in questionable sources or sources of dubious value should not be used, either as a source or as an external link (see above).
Never use self-published books, zines, websites, webforums, blogs and tweets as a source for material about a living person, unless written or published by the subject of the biographical material (see below). "Self-published blogs" in this context refers to personal and group blogs. Some newspapers host interactive columns that they call blogs, and these may be acceptable as sources so long as the writers are professionals and the blog is subject to the newspaper's full editorial control. Where a news organization publishes the opinions of a professional but claims no responsibility for the opinions, the writer of the cited piece should be attributed (e.g., "Jane Smith has suggested..."). Posts left by readers may never be used as sources.[1]
Avoid repeating gossip. Ask yourself whether the source is reliable; whether the material is being presented as true; and whether, even if true, it is relevant to an encyclopedia article about the subject. When less-than-reliable publications print material they suspect is untrue, they often include weasel phrases and attributions to anonymous sources. Look out for these. If the original publication doesn't believe its own story, why should we?
Be wary of "feedback loops" in which an unsourced and speculative contention in a Wikipedia article gets picked up, with or without attribution, in an otherwise-reliable newspaper or other media story, and that story is then cited in the Wikipedia article to support the original speculative contention.
Statements of opinion
Some sources may be considered reliable for statements as to their author's opinion, but not for statements of fact. A prime example of this are Op-ed columns that are published in mainstream newspapers. When discussing what is said in such sources, it is important to directly attribute the material to its author, and to do so in the main text of the Wikipedia article so readers know that we are discussing someone's opinion.
There is, however, an important exception to sourcing statements of opinion: Never use self-published books, zines, websites, webforums, blogs and tweets as a source for material about a living person, unless written or published by the subject of the biographical material. "Self-published blogs" in this context refers to personal and group blogs (see: WP:BLP#Sources and WP:BLP#Using the subject as a self-published source).
Note that otherwise reliable news sources--for example, the website of a major news organization--that happens to publish in a "blog" style format for some or all of it's content may be considered to be equally reliable as if it were published in a more "traditional" 20th-century format of a classic news story. However, the distinction between "opinion pieces" and news should be considered carefully.
Are weblogs reliable sources?
In many cases, no. Most private weblogs ("blogs"), especially those hosted by blog-hosting services such as Blogger, are self-published sources; many of them published pseudonymously. There is no fact-checking process and no guarantee of quality of reliability. Information from a privately-owned blog may be usable in an article about that blog or blogger under the self-publication provision of the verifiability policy.
Weblog material written by well-known professional researchers writing within their field, or well-known professional journalists, may be acceptable, especially if hosted by a university, newspaper or employer (a typical example is Language Log, which is already cited in several articles, e.g. Snowclone, Drudge Report). Usually, subject experts will publish in sources with greater levels of editorial control such as research journals, which should be preferred over blog entries if such sources are available.
Blogs may be used in certain conditions as secondary sources on living persons; see WP:BLP.

Things to considerEdit

Is the article you're sourcing via a blog of a non-biographical nature (i.e., about computer science? Cooking? History about deceased individuals?) from a website that is known in the relevant subject circles as a source or authority? If the specific author of the specific blog post an expert or authority? In either case, the blog post may be fine to use.

Is the article you're sourcing via a blog of a biographical nature, about a living person? If so, is the blog hosted on a reputable news website? Is the news source in question typically fine to use on Wikipedia on other biographical articles as a source? Is the author a journalist? Is the blog post just a quick--or detailed--news report that happens to be technically formatted as a blog post? If you can answer yes to each of these questions, the source is probably fine to use in a BLP. If the post is expressing an opinion of a named individual, rather than a pure news source, the content added to our BLP article must be attributed to the specific speaker or writer. Such as, "According to James Smith..."